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Registered Member #2161
Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247
Hello everyone,
A couple of questions have popped up in my mind, so here goes:
1. What would be the best way to prevent the surge of current induced by large electrolytic caps that are run in these systems, at >500uF popping breakers occur far to regularly. I was thinking of using a ~20W 15-30ohm resistor in conjunction with a switch and led or just a 150T charging choke on a powdered metal core? Any suggestions on this one? As I have no variac this is a must for my upcoming project.
2. How do DRSSTC systems behave in regards to secondary heating? In my CW coils quite a lot of secondary heat is produced. The main reason I ask is that the secondary I plan on using for my next project is rolled on LDPE, great as far as RF absorption is concerned, but horrible as far as thermal stability is concerned.
3. Does anyone know of a source for DRSSTC PCB's? I am looking at something along the lines of Steve Ward's various version with OCD. If I can't find one, then i'll just make it on a good ole protoboard, I ask for the sake of making the build more professional looking and the fact that my free time has been dropping considerably. -.-
Registered Member #2390
Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381
Here goes! I am new to this subject so i will keep it limited. 1) Not sure, not experienced enough. Possibly using a large spool of wire in series with your power connection to the coil. 2) Can't answer that one. 3) Eastern voltage research sells a PCB kit for Dan's minibrute with a schematic and parts list. It does have ocd as well as primary feedback. So far i have had great luck with it. That is one of them in my avatar photo. Anyway, best of luck to you and happy building!!
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
brtaman wrote ...
Hello everyone,
A couple of questions have popped up in my mind, so here goes:
1. What would be the best way to prevent the surge of current induced by large electrolytic caps that are run in these systems, at >500uF popping breakers occur far to regularly. I was thinking of using a ~20W 15-30ohm resistor in conjunction with a switch and led or just a 150T charging choke on a powdered metal core? Any suggestions on this one? As I have no variac this is a must for my upcoming project.
2. How do DRSSTC systems behave in regards to secondary heating? In my CW coils quite a lot of secondary heat is produced. The main reason I ask is that the secondary I plan on using for my next project is rolled on LDPE, great as far as RF absorption is concerned, but horrible as far as thermal stability is concerned.
3. Does anyone know of a source for DRSSTC PCB's? I am looking at something along the lines of Steve Ward's various version with OCD. If I can't find one, then i'll just make it on a good ole protoboard, I ask for the sake of making the build more professional looking and the fact that my free time has been dropping considerably. -.-
1. You can simply use a resistor in series with your cap bank that switches in and out via a relay. This is very common and used commercially in all sorts of amps, appliances, power supplies, etc... I'm sure a schematic exists on google somewhere.
2. Don't worry about secondary material. It has practically NO affect on your output. Really. Usually the armchair tesla coilers claim you need a special coilform for maximum performance, but in my experience whether you use PVC, acrylic, wood, cardboard, or whatever, its all the same.
3. I have plans and boards for a nice miniBrute DRSSTC system on my website at Yeah i know - selfless self promotion!
If you are looking for some simple DRSSTC designs, than I would recommend visiting Steve Ward's site. He has lots of great DRSSTC stuff!
Registered Member #2161
Joined: Fri Jun 05 2009, 03:36PM
Location:
Posts: 247
Thanks for the replies, everyone.
doc electrons: the TC is looking good! Just bought some plexi-glass myself, it was a bit more expensive than I had thought though.
arc: yeah that is what I was thinking as well, going to use a standard choke for the time being. Thanks for the heads-up regarding heating.
Dr. Gigavolt: Great idea, the relay combined with the resistor definitely seems to be the optimum solution, will look into it and post, when I find a good schematic. I agree with the secondary material part, with the power we are pushing through these coils, more energy gets wasted in primary heating alone then with material absorbency, I "might" get en extra 5mm of sparks. To be honest, I just picked up the first tube that looked decent at the local hardware store, it had a "4" on it which meant nothing to me, found out later that its LDPE. On another note, I have been looking through your site and the mini-brute is definitely a class-a DRSSTC system.8-)
Mads: You have PM.
Extra questions have popped up during testing;-):
I have been testing a CT I made using a 15k Al ferrite core (overkill, but only one I had on me). How did you guys manage not to blow up the bridge every other arc strike on the first gen DRSSTC systems? The signal goes from a nice sine-wave to a lego sculpture as soon as I draw an arc? I can see it surviving in a PLL system, but wouldn't a 74HC14 would completely lose the signal?
Another question that has been bugging me is using a CT on the primary for a feedback signal. How is it possible to keep in tune and keep the driver resonating at the resonant frequency of the secondary, if we are not getting feedback from it, but from the power part? Isn't it like trying to keep score of a football game that you are not watching?
Does anyone have a source for spun-alu torroids in Europe? Cross-Atlantic shipping is a killer.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Hi, I use this circuit as a soft-start. you calculate the series cap (labeled "X2" in the schematic) to supply the right amount of current into the relay, and the electrolytic cap in parallel to the relay coil sets delay time (should be something 1/4 a second)
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
here is Steve wards new driver that works good
It depends on how much of a chalenge you want. I took Steve's design and build my own PCB with expresspcb witch has a free download or you can take the eagal layout and have them built. express pcb has a mini board layout (about 62 for 3 PCB's with shipping) and accecepts many formats and is competitve. I have not tried futurelec yet but I plan to.
if you want less hasle Dr. GigaVolt has what you want and has a a compleat set of insructions and is good for the beginer
Registered Member #1617
Joined: Fri Aug 01 2008, 07:31AM
Location: Adelaide, South Australia
Posts: 139
I have been testing a CT I made using a 15k Al ferrite core (overkill, but only one I had on me). How did you guys manage not to blow up the bridge every other arc strike on the first gen DRSSTC systems? The signal goes from a nice sine-wave to a lego sculpture as soon as I draw an arc? I can see it surviving in a PLL system, but wouldn't a 74HC14 would completely lose the signal?
I think that the 74hc14 style driver with CT relies on the CT being able to produce a large amplitude sineish sort of wave (or lego block wave) wave, then hard-limiting it with clamping diodes to get an aproximately nice square wave.
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Couple DR/SSTC Questions
To be honest, I just picked up the first tube that looked decent at the local hardware store, it had a "4" on it which meant nothing to me, found out later that its LDPE. On another note, I have been looking through your site and the mini-brute is definitely a class-a DRSSTC system.8-)
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